EP4069648A1

EP4069648A1 - Sludge trap container

Info

Publication number: EP4069648A1
Application number: EP20820587.2A
Authority: EP
Inventors: Joakim Ambrosson; Martin Lans; Rikard Andskär
Original assignee: Fann Va Teknik AB
Current assignee: Fann Va Teknik AB
Priority date: 2019-12-03
Filing date: 2020-12-01
Publication date: 2022-10-12
Also published as: WO2021112745A1

Abstract

The present invention relates to a sludge trap container (12) comprising a first chamber (21), a second chamber (22) and a third chamber (23). The first (21), second (22), and third chamber (23) are independent units that are assembled to form a sludge trap container (12). A first portion of the matching wall (214a) of the first chamber (21) is connected to the first matching wall (222) of the second chamber (21), the connected matching walls forming a first double-walled inner wall (321). A second portion of the matching wall (214b) of the first chamber (21) is connected to the first matching wall (235) of the third chamber (23), the connected matching walls forming a second double-walled inner wall (322). The second matching wall (224) of the second chamber (22) is connected to the second matching wall (232) of the third chamber (23), the connected walls forming a third double-walled inner wall (323).

Description

SLUDGE TRAP CONTAINER

Field of the invention

The present invention relates to a domestic tank system, and more particularly to a sludge trap container as well as a method for the production of such a sludge trap container and a kit for forming such a sludge trap container.

Background of the invention

Water from a domestic septic tank system contains fat, organic matter, particles, dissolved ammonium, pathogens etc. and needs to be treated prior to being returned to the groundwater. This is normally done in two sequential steps:

1. Mechanical treatment, e.g. in a sludge trap container, a three-chambered treatment tank etc., wherein fat and solid particles are separated out.

2. Biological treatment, i.e. an infiltration station wherein the water is filtrated into the ground. In this step the water is purified from organic matter, dissolved ammonium etc. This can also be achieved using a sandfilter bed.

In the mechanical treatment step solid particles and fat are separated from the septic water, solid particles sink to the bottom and fat and light particles (e.g. paper) float (scum) to the top and the middle clarified part of the septic water is transported to the biological treatment step.

There may be an additional third step after step 1 and 2 described above in which phosphorous is removed from the septic water.

One common design of sludge trap containers is to have three separate chambers. In such a sludge trap container the septic water enters the first chamber and then continues to the second and last the third. From the third chamber the clarified phase is transported to the biological treatment step. In such a design comprising three chambers it is of importance that the inner walls, i.e. the ones separating the different chambers, are structurally stable. This may be achieved for example by two inner walls with a volume of air in between, or by building inner walls inside one chamber dividing into three parts. In the latter case the inner walls are built inside the container after manufacturing making the working environment very narrow and there is a considerable risk that the inner walls are unstable.

The common design containing three separated chambers are most often fabricated in one independent unit. This means that if there is a need for one chamber to be of another size, bigger or smaller, the entire three-chambered unit must be fabricated again.

SE5229220 C2 discloses a sludge trap container having at least one inlet and at least two outlets, in connection with the outlets there are flow regulators configured to regulate the amount of water that flows from the outlets.

FR2862886 A1 discloses a module of a tank for the purification of wastewater which is obtained by molding of plastic material. The module comprises side walls, wherein one of the side walls has a support portion allowing the joining of two modules joined to one another.

In the prior art there is a need for a sludge trap container that is structurally stable while limiting the amount of dead volume in the construction.

Summary of the invention

The object of the invention is to provide a sludge trap container that overcomes at least some of the drawbacks of the prior art. This is achieved by the sludge trap container as defined in claim 1, the system as defined in claim 12, the kit as defined in claim 13 and the method as defined in claim 18.

In one aspect of the invention there is a sludge trap container comprising a first chamber, a second chamber, and a third chamber, an inlet for receiving septic water arranged in the first chamber, and an outlet for outputting the clarified phase arranged in the third chamber, wherein the first chamber, the second chamber, and the third chamber are arranged to be in fluid communication. The first, second, and third chamber, each are independent units, and wherein the first chamber comprises a matching wall, the second chamber comprises a first matching wall and a second matching wall, and the third chamber comprises a first matching wall and a second matching wall. A first portion of the matching wall of the first chamber is connected to the first matching wall of the second chamber and the connected matching walls form a first doubled-walled inner wall. A second portion of the matching wall of the first chamber is connected to the first matching wall of the third chamber and the connected matching walls form a second doubled-walled inner wall. The first doubled-walled inner wall is arranged adjacent to the second doubled-walled inner wall along the plane of the matching wall of the first chamber and the second matching wall of the second chamber is connected to the second matching wall of the third chamber and the connected matching walls form a third doubled-walled inner wall of the sludge trap container.

According to one aspect of the invention the matching wall of the first chamber and the first matching wall of the second chamber are on their outer edges joined by a first circumferential joint, the matching wall of the first chamber and the first matching wall of the third chamber are on their outer edges joined by a second circumferential joint, and the second matching wall of the second chamber and the second matching wall of the third chamber are on their outer edges joined by a third circumferential joint.

According to one aspect of the invention the first circumferential joint and the second circumferential joint forms a continuous joint around the outer edge of the matching wall of the first chamber.

According to one aspect of the invention the first circumferential joint is a weld, the second circumferential joint is a weld and the third circumferential joint is a weld.

According to one aspect of the invention the thickness of the doubled-walled inner walls is 5-50 mm.

According to one aspect of the invention the first chamber and the second chamber are connected via a first protruding pipe extending from the matching wall of the first chamber and fitted in a first opening at the first matching wall of the second chamber, and the second chamber and the third chamber are connected via a second protruding pipe extending from the second matching wall of the third chamber and fitted in a second opening at the second matching wall of the second chamber.

According to one aspect of the invention the first chamber, the second chamber, and the third chamber are fabricated as independent and separate units. Thanks to the invention that the chambers may be fabricated in independent units, this enables the standardization of two units while the third may be custom-made depending on the size of the household.

It is an advantage of the invention that the double walls separating the chambers are structurally stable.

It is a further advantage of the invention that it contains less dead volume as compared to the prior art making it more volume efficient.

According to one aspect the sludge trap container according to the invention is composed of plastic. In a specific example the sludge trap container is composed of polyethylene.

It is an advantage of the invention that it is made of plastic which is a light and durable material in comparison with e.g. concrete. This makes is easier to handle upon installation.

It is a further advantage of the invention that sludge trap containers according to the invention are stackable.

According to one aspect of the invention the matching wall of the first chamber, the first matching wall of the second chamber and the first matching wall of the third chamber each comprises locating grooves.

According to one aspect of the invention the sludge trap container further comprises a T-shaped enforcing member.

It is an advantage with the locating grooves that they provide extra stability to the sludge trap container.

In one aspect of the invention there is a domestic septic tank system a sludge trap container.

In one aspect of the invention there is a kit comprising a first chamber comprising an inlet, a second chamber, and a third chamber comprising an outlet to be assembled to a sludge trap container, wherein a first portion of the matching wall of the first chamber is to be connected to the first matching wall of the second chamber and a second portion of the matching wall of the first chamber is to be connected to the first matching wall of the third chamber, the first matching wall of the second chamber are to be arranged adjacent to the first matching wall of the third chamber along the plane of the matching wall of the first chamber, and wherein the second matching wall of the second chamber is to be connected to the second matching wall of the third chamber, and wherein when the first portion of the matching wall of the first chamber is combined with the first matching wall of the second chamber forming a first doubled-walled inner wall, and when the second portion of the matching wall of the first chamber combined with the first matching wall of the third chamber forming a second doubled-walled inner wall, and when the second matching wall of the second chamber is combined with the second matching wall of the third chamber forming a third doubled-walled inner wall of the sludge trap container.

According to one aspect of the invention there is a kit wherein the matching wall of the first chamber and the first matching wall of the second chamber are to be joint together at their outer edges by a first circumferential weld, and the matching wall of the first chamber and the first matching wall of the third chamber are to be joint together at their outer edges by a second circumferential weld, and the second matching wall of the second chamber and the second matching wall of the third chamber are to be joint together by a third circumferential weld.

According to one aspect of the invention there is a kit wherein the first circumferential weld and the second circumferential weld are to form a continuous weld around the outer edges of the matching wall of the first chamber.

According to one aspect of the invention there is a kit, wherein the matching wall of the first chamber, the first matching wall and the second matching wall of the second chamber and the first matching wall and the second matching wall of the third chamber each comprises locating grooves.

According to one aspect of the invention there is a kit, wherein the first chamber has a larger volume than the second chamber, and than the third chamber.

In one aspect of the invention there is a method of manufacturing a sludge trap container comprising the steps of:

- manufacturing a first chamber, a second chamber and a third chamber as independent and separate units, and wherein the first chamber comprises a matching wall, the second chamber comprises a first matching wall and a second matching wall, and the third chamber comprises a first matching wall and a second matching wall;

- assembling the first chamber, the second chamber and the third chamber so that a first portion of the matching wall of the first chamber is connected to the first matching wall of the second chamber, the connected matching walls forming a first doubled-walled inner wall, a second portion of the matching wall of the first chamber is connected to the first matching wall of the third chamber, the connected matching walls forming a second doubled-walled inner wall, and wherein the first doubled-walled inner wall is arranged adjacent to the second doubled- walled inner wall along the plane of the matching wall of the first chamber, the second matching wall of the second chamber is connected to the second matching wall of the third chamber, the connected matching walls forming a third doubled-walled inner wall of the sludge trap container,

- joining the matching wall of the first chamber and the first matching wall of the second chamber on their outer surfaces by a first circumferential joint; and

- joining the matching wall of the first chamber and the first matching wall of the third chamber on their outer edges by a second circumferential joint; and

- joining the second matching wall of the second chamber and the second matching wall of the third chamber on their outer edges by a third circumferential joint.

According to one aspect of the method of the invention the matching wall of the first chamber and the first matching wall of the second chamber are on their outer surfaces welded by a first circumferential weld, and the matching wall of the first chamber and the first matching wall of the third chamber are on their outer edges welded by a second circumferential weld, and the second matching wall of the second chamber and the second matching wall of the third chamber are on their outer edges welded by a third circumferential joint. According to one aspect of the method of the invention the first chamber, the second chamber and the third chamber are manufactured as independent and separate units using rotational casting.

According to one aspect of the method of the invention the step of assembling the first chamber with the second chamber and the third chamber comprises using locating grooves that are provided on the matching walls.

All the embodiments described herein are applicable to all the aspects of the present invention unless expressly stated otherwise. In the following, the invention will be described in more detail, by way of example only, with regard to non-limiting embodiments thereof, reference being made to the accompanying drawings.’

Brief description of the drawings

Fig. 1 is a schematic illustration of domestic water sewage system having means for infiltrating the treated water into the ground;

Fig. 2a-c are schematic illustrations of the sludge trap container according to the invention wherein a) is an exploded view of a sludge trap container according to the invention, b) is an elevated view of an assembled sludge trap container according to the invention and c) is a cross sectional view of an assembled sludge trap container according to the invention;

Fig. 3 is an elevated view of an assembled sludge trap container according to one embodiment of the invention; and

Fig. 4 is a schematic illustration of the flow paths in a cross-sectional view of a sludge trap container according to one embodiment of the invention.

Detailed description

Terms such as “top”, “bottom”, “upper”, “lower” etc. are used merely to the geometry of the embodiment of the invention showed in the drawings and are not intended to limit the invention in any manner.

As described in the background a sludge trap container according to the invention may be part of a domestic septic tank system 10 as the one illustrated in Figure 1, comprising a household 11, a sludge trap container 12, a treatment bed 13 and a distribution pipe 14. Septic water from the household enters the sludge trap container 12 in the first chamber 21 in which solid particles and fats are removed after which the clarified phase exists the sludge trap container 12 in the third chamber 23 and enters the distribution pipe 14.

A sludge trap container 12 according to the invention is schematically depicted in Figure 2 a-c, wherein a) is an exploded view also representing the different parts of the sludge trap container 12 prior to assembling, b) is an elevated view of the assembled sludge trap container 12 and c) is a cross sectional view of the assembled sludge trap container 12. The sludge trap container 12 comprises a first chamber 21, a second chamber 22 and a third chamber 23 that are separate and independent units, the chambers 21; 22; 23 are assembled to form a sludge trap container 12. The first chamber 21 is schematically depicted in Figures 2a and c. The first chamber 21 comprises an outer wall 212 and a matching wall 214. The outer wall 212 is typically curved, and the matching wall 214 is typically planar. The first chamber 21 further comprises an inlet 211 located at the upper part of the outer wall 212. The inlet 211 receives the septic water from the household 11. The first chamber 21 further comprises a first protruding pipe 213 extending from a first portion 214a of the matching wall 214. The first protruding pipe 213 is located at the upper half of the matching wall 214. The length of the first protruding pipe 213 is typically 80-120 mm, such as 110 mm. The first chamber 21 further comprises an opening 611 at the top for inspection and waste removal. The outer wall 212 and the matching wall 214 are joined with a top and a bottom to form a closed first chamber 21.

The second chamber 22 is schematically depicted in Figures 2a and c. The second chamber 22 comprises a first matching wall 222, a second matching wall 224 and an outer wall 225. The outer wall 225 is typically curved, and the first 222 and second 224 matching wall is typically planar. The second chamber 22 further comprises a first opening 221 located at the first matching wall 222, and a second opening 223 located at the second matching wall 224. The second chamber 22 further comprises an opening 612 at the top for inspection and waste removal. The outer wall 225, the first matching wall 222 and the second matching wall 224 are joined with a top and a bottom to form a closed second chamber 22.

The third chamber 23 is schematically depicted in Figures 2a and c. The third chamber 23 comprises a first matching wall 232, a second matching wall 235, and an outer wall 234. The outer wall 234 is typically curved, and the first 232 and the second 235 matching wall is typically planar. The third chamber 23 further comprises a second protruding pipe 231 located at the first matching wall 232. The length of the second protruding pipe 231 is typically 140-180 mm, such as 160 mm. The third chamber 23 further comprises an outlet 233, located the outer wall 234. The outlet 233 is positioned at the upper half of the third chamber 23. The outlet 233 outputs the clarified phase from the sludge trap container 12. The third chamber 23 further comprises an opening 613 at the top for inspection and waste removal. The outer wall 234, the first matching wall 232 and the second matching wall 235 are joined with a top and a bottom to form a closed third chamber 23. The sludge trap container 12, schematically depicted in Figure 2 b, has been formed by assembling the first chamber 21 with the second chamber 22 and the third chamber 23. In the sludge trap container 12 the first portion of the matching wall 214a of the first chamber 21 is connected to the matching wall 221 of the second chamber forming a first double-walled inner wall 321. The second portion of the matching wall 214b of the first chamber 21 is connected to the first matching wall 235 of the third chamber 23 forming a second doubled-walled inner wall 322. The first double-walled inner wall 321 is arranged adjacent to the second double-walled inner wall 322 along the plane of the matching wall 214 of the first chamber 21. The second matching wall 224 of the second chamber 22 is connected to the second matching wall 232 of the third chamber 23 forming a third doubled-walled inner wall 323. Further, in the sludge trap container 12 the first protruding pipe 213 extending from the first portion of the matching wall 214a of the first chamber 21 is fitted in a first opening 221 at the first matching wall 222 of the second chamber 22, so that the first chamber 21 and the second chamber 22 are in fluid communication. The second protruding pipe 231 extending from the second matching wall 232 of the third chamber 23 is fitted in the second opening 223 of the second chamber 22, so that the second chamber 22 and the third chamber 23 are in fluid communication. In the sludge trap container, the opening 611 at the first 21 chamber, the opening 612 at the second chamber 22 and the opening 613 at the third chamber 23 for inspection and waste removal has preferably been joined to form a combined opening. Such an arrangement wherein the three chambers 21; 22; 23 are joint together so that a T-shape is created by the inner walls 321; 322; 323, when seen in cross-section, adds to the stability of the sludge trap container 12. The T-shape of the inner walls 321; 322; 323 can for example allow for the sludge trap container 12 to be transported and uplifted without the risk of breaking. Additionally, it may allow the sludge container 12 to be stacked on top of another sludge trap container 12, i.e. to be stackable.

In an embodiment, instead of the protruding pipes 213; 231 extending from the first chamber 21 and the third chamber 23, the protruding pipes 213; 231 extends from the second chamber 22. In such embodiment the first chamber 21 and the third chamber 23 each comprises an opening 222; 223. In an embodiment of the sludge trap container 12, Figure 2 c, the first 21, second 22 and third 23 chambers are joint together by a joint at the outer edges of the matching walls 214; 222; 224; 232; 235. The first portion of the matching wall 214 of the first chamber 21 and the first matching wall 222 of the second chamber 22 are joint on their outer edges by a first circumferential joint 411 sealing the first doubled-walled inner wall 321. The second portion of the matching wall 214 of the first chamber 21 and the first matching wall 235 of the third chamber 23 are joint on their outer edges by a second circumferential joint 412, sealing the second doubled-walled inner wall 322. The second matching wall 224 of the second chamber 22 and the second matching wall 232 of the third chamber 23 are joint on their outer edges by a third circumferential joint 413, sealing the third doubled- walled inner wall 323. In an embodiment the first circumferential joint 411 and the second circumferential joint 412 form a continuous joint around the outer edge of the matching wall 214 of the first chamber 21. The joint may be a weld, a sealant, a flexible strip combined with a sealant or adhesive or a flexible tubing combined with a sealant or adhesive. The sealed doubled-walled inner walls 321; 322; 323 form a closed space of the interior of the doubled-walled inner walls 321; 322; 323. Hence, the joints have dual functions of joining the separate first 21; second 22, and third chamber 23 together, and sealing the interior of the doubled-walled inner walls 321; 322; 323 from the outside. As previously discussed, inner walls 321; 322; 323 forms a stabilizing T-shape. The stabilizing effect is further enhanced by the circumferential joints 411, 412, 413. A T-shaped enforcing member 415, schematically illustrated in Figure 2d is formed by the first portion of the matching wall 214a of the first chamber 21, the first matching wall 222 of the second chamber 22 and the first circumferential joint 411; combined with the second portion of the matching wall 214b of the first chamber 21 and the first matching wall 235 of the third chamber 23 and the second circumferential joint 412; and combined with the second matching wall 224 of the second chamber 22, the second matching wall 232 of the third chamber 23 and the third circumferential joint 413.

In an embodiment the first chamber 21, second chamber 22 and third chamber 23 forms a kit. The kit is to be assembled to a sludge trap container 12 at a site different from the production site, e.g. the site of installation. During use of the sludge trap container 12, septic water enters into the first chamber 21 via the inlet 211, and continues to the second chamber 22 via the first protruding pipe 213 extending from the first portion of the matching wall 214a of the first chamber 21, and last to the third chamber 23 via the second protruding pipe 231 extending from the second matching wall 232 of the third chamber 23. In all three chambers 21; 22; 23 the septic water is treated by that solid particles sink to the bottom and fat and light particles (e.g. paper) float (scum) to the top and the middle, clarified, phase of the septic water is transported further. From the third chamber 23 the clarified phase is transported to the distribution pipe 14 via the outlet 233, and from the distribution pipe 14 to the treatment bed 13. The transportation from the third chamber 23 may occur in any suitable way e.g. via gravity, or via an integrated pump.

The flow path of the septic water inside the sludge trap container 12 is directed by the positions of the protruding pipes 213; 231, the inlet 211, and the outlet 233. In order for the treatment of the septic water inside the sludge trap container 12 to be as efficient as possible the flow path should be as long as possible. In one embodiment the inlet 211 is arranged at the upper part of the first container 12. As discussed above, the first protruding pipe 213 is arranged to direct the flow from the first chamber 21 to the second chamber 22. The first protruding pipe 213 is arranged at the outer corner of the second chamber 22 and at the upper half of the sludge trap container 12. The second protruding pipe 231 is arranged to direct the flow from the second chamber 22 to the third chamber 23. The second protruding pipe 231 is arranged at the inner corner of the third chamber 23 and at the lower half of the sludge trap container 12. The outlet 233 is arranged at the upper part of the third chamber 23. The above described arrangement of the protruding pipes 213; 231, the inlet 211, and the outlet 233 is advantageous since it increases the length of the flow inside the sludge trap container 12. A flow path formed by such an arrangement is schematically illustrated by arrows in Figure 4. A long flow path allows the septic water to be in the sludge trap container 12 for a longer time period, which allow for a more complete treatment process. In one embodiment (not shown) the flow of the septic water can be further directed by a pipe extending from the inlet 211 into the first chamber 21 , and possible also a pipe extending from the outlet 233 into the third chamber 23. In one embodiment the first protruding pipe 213 extending from the first portion of the matching wall 214a of the first chamber 21 is arranged at the outer corner of the sludge trap container 12. The first protruding pipe is arranged at 65 % of the total heigh (or 550-580 mm) from the bottom of the sludge trap container 12, and 100-120 mm from the outer wall 225 of the second chamber 22. The second protruding pipe 231 extending from the second matching wall 232 of the third chamber 23 is arranged at inner corner of the third chamber 23. The second protruding pipe 231 is arranged 35 % (or 350-380 mm) of the total heigh from the bottom of the sludge trap container 12, and 130-170 mm from the matching wall 214. The first protruding pipe 213 extends 110 mm from the first portion of the matching wall 214a of the first chamber 21 into the second chamber 22, and the second protruding pipe 231 extends 160 mm from the second matching wall 232 of the third chamber 23 into the second chamber 22.

The three chambers 21; 22; 23 are fabricated separately as independent units and may therefore be provided in different sizes. In a conventional sludge trap container 12 the first chamber 21 is larger than the second 22 and the third chamber 23. The chambers 21; 22; 23 of a typical sludge trap container 12 may have a volume of 2- 10 m³.

The sludge trap container 12 may be fabricated in plastic, preferably polyethylene or another suitable plastic. The three chambers 21; 22; 23 may be fabricated using rotational casting.

In one embodiment the three chambers 21; 22; 23 are provided with locating grooves 510 at their respective matching walls 214; 222; 224; 232; 235. In such case the locating grooves 510 are used to connect the matching walls 214; 222; 224; 232; 235 with each other as described earlier. The number of locating grooves 510 can for example be 2-4 per matching wall 214; 222; 224; 232; 235. Furthermore, the locating grooves 510 provides mechanical stability to the sludge trap container 12, in particular to the inner walls 321; 322; 323. The locating grooves 510 provided at the matching walls 214; 222; 224; 232; 235 allow for the formation of a double corrugated structure at the inner walls 321; 322; 323 which is stable. The locating groves 510 can be seen in Figure 2a. In one embodiment four locating grooves are arranged at the matching wall 214 of the first chamber 21, and two locating grooves 510 are arranged at each of the matching walls 222; 224; 232; 235 of the second 22 and third chamber 23. In one embodiment the locating grooves 510 are arranged so that they are not located at the site of the intersection of the inner walls 321; 322; 323. In one embodiment the locating grooves 510 are part of the T-shaped enforcing member 415.

In an embodiment the sludge trap container 12 comprises stiffening grooves 610 on the outer walls 212; 225; 234, Figure 3. This provides extra structural stability to the sludge trap container 12.

The method of manufacturing a sludge trap container 12 comprises the steps of: manufacturing a first chamber 21, a second chamber 22 and a third chamber 23 as independent and separate units, wherein the first chamber 21 comprises a matching wall 214, the second chamber 22 comprises a first matching wall 222 and a second matching wall 224, and the third chamber comprises a first matching wall 235 and a second matching wall 232; assembling the first chamber 21, the second chamber 22 and the third chamber 23 so that: a first portion of the matching wall 214a of the first chamber 21 is connected to the first matching wall 222 of the second chamber 22, the connected matching walls forming a first doubled-walled inner wall 321; a second portion of the matching wall 214b of the first chamber 21 is connected to the first matching wall 235 of the third chamber, the connected matching walls forming a second doubled-walled inner wall 322, and wherein the first doubled-walled inner wall 321 is arranged adjacent to the second doubled-walled inner wall 322 along the plane of the matching wall 214 of the first chamber 21 ; and the second matching wall 224 of the second chamber 22 is connected to the second matching wall 232 of the third chamber 23, the connected matching walls forming a third doubled-walled inner wall 323 of the sludge trap container 12;

- joining the matching wall 214 of the first chamber 21 and the first matching wall 222 of the second chamber 22 on their outer surfaces by a first circumferential joint 411; - joining the matching wall 214 of the first chamber 21 and the first matching wall 235 of the third chamber 23 on their outer edges by a second circumferential joint 412; and

- joining the second matching wall 224 of the second chamber 22 and the second matching wall 232 of the third chamber 23 on their outer edges by a third circumferential joint 413.

In an embodiment of the method the matching walls 214; 222; 224; 232; 235 are joint by welding. In an embodiment of the method the matching walls 214; 222; 224; 232; 235 comprises locating grooves 510. The locating grooves 510 are used during the assembling of the first chamber 21 with the second 22 and third chamber 23.

The first chamber 21, the second chamber 22 and the third chamber 23 are in an embodiment of the method fabricated using rotational casting.

The present invention is not limited to the above-described embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1. A sludge trap container (12) comprising a first chamber (21), a second chamber (22), and a third chamber (23), an inlet (211) for receiving septic water arranged in the first chamber (21), and an outlet (233) for outputting the clarified phase arranged in the third chamber (23), wherein the first chamber (21), the second chamber (22), and the third chamber (23) are arranged to be in fluid communication, characterized in that the first (21), second (22), and third chamber (23), each are independent units, and wherein the first chamber (21) comprises a matching wall (214), the second chamber (22) comprises a first matching wall (222) and a second matching wall (224), and the third chamber comprises a first matching wall (235) and a second matching wall (232), and wherein a first portion of the matching wall (214a) of the first chamber (21) is connected to the first matching wall (222) of the second chamber (22) and the connected matching walls forming a first doubled-walled inner wall (321); a second portion of the matching wall (214b) of the first chamber (21) is connected to the first matching wall (235) of the third chamber (23) and the connected matching walls forming a second doubled-walled inner wall (322), wherein the first doubled-walled inner wall (321) is arranged adjacent to the second doubled-walled inner wall (322) along the plane of the matching wall (214) of the first chamber (21); and wherein the second matching wall (224) of the second chamber (22), is connected to the second matching wall (232) of the third chamber (23) and the connected matching walls forming a third doubled-walled inner wall (323) of the sludge trap container (12).

2. The sludge trap container (12) according to claim 1, wherein the first portion of the matching wall (214a) of the first chamber (21 ) and the first matching wall (222) of the second chamber (22) are on their outer edges joined by a first circumferential j oint (411); the second portion of the matching wall (214b) of the first chamber (21) and the first matching wall (235) of the third chamber (23) are on their outer edges joined by a second circumferential joint (412); and the second matching wall (224) of the second chamber (22) and the second matching wall (232) of the third chamber (23) are on their outer edges joined by a third circumferential joint (413).

3. The sludge trap container (12) according to claim 2, wherein the first circumferential joint (411) and the second circumferential joint (412) forms a continuous joint around the outer edge of the matching wall (214) of the first chamber (21).

4. The sludge trap container (12) according to claim 2 or 3, wherein the first circumferential joint (411) is a weld, the second circumferential joint (412) is a weld and the third circumferential joint (413) is a weld.

5. The sludge trap container (12) according to any of the preceding claims, wherein the thickness of the doubled-walled inner walls (321; 322; 323) is 5- 50 mm.

6. The sludge trap container (12) according to any of the preceding claims, wherein the first chamber (21) and the second chamber (22) are connected via a first protruding pipe (213) extending from the first portion of the matching wall (214a) of the first chamber (21) and fitted in a first opening (221) at the first matching wall (222) of the second chamber (22), and the second chamber (22) and the third chamber (23) are connected via a second protruding pipe (231) extending from the second matching wall (232) of the third chamber (23) and fitted in a second opening (223) at the second matching wall (224) of the second chamber (22).

7. The sludge trap container (12) according to any of the preceding claims, wherein the sludge trap container 12 is composed of plastic.

8. The sludge trap container (12) according to claim 7, wherein the sludge trap container (12) is composed of polyethylene.

9. The sludge trap container (12) according to any of the preceding claims, wherein the first chamber (21), the second chamber (22), and the third chamber (23) are fabricated as independent and separate units.

10. The sludge trap container (12) according to any of the preceding claims, wherein the matching wall (214) of the first chamber (21), the first matching wall (222) of the second chamber (22) and the first matching wall (235) of the third chamber (23) each comprises locating grooves (510).

11. The sludge trap container (12) according to any of the preceding claims, wherein the sludge trap container (12) further comprises a T-shaped enforcing member (415).

12. A domestic septic tank system (10) comprising the sludge trap container (12) according to any of the preceding claims.

13. A kit comprising a first chamber (21) comprising an inlet (211), a second chamber (22), and a third chamber (23) comprising an outlet (233) to be assembled to a sludge trap container (12); wherein a first portion of the matching wall (214a) of the first chamber (21) is to be connected to the first matching wall of the second chamber (22) and a second portion of the matching wall (214b) of the first chamber (21) is to be connected to the first matching wall (235) of the third chamber (23), the first matching wall (222) of the second chamber (22) are to be arranged adjacent to the first matching wall (235) of the third chamber (23) along the plane of the matching wall (214) of the first chamber (21); and wherein the second matching wall (224) of the second chamber (22) is to be connected to the second matching wall (232) of the third chamber (23); and wherein when the first portion of the matching wall (214a) of the first chamber (21) is combined with the first matching wall (222) of the second chamber (22) forming a first doubled-walled inner wall (321), and when the second portion of the matching wall (214b) of the first chamber (21) combined with the first matching wall (235) of the third chamber (23) forming a second doubled-walled inner wall (322), and when the second matching wall (224) of the second chamber (22) is combined with the second matching wall (224) of the third chamber (23) forming a third doubled-walled inner wall (323) of the sludge trap container (12).

14. The kit according to claim 13 wherein the first portion of the matching wall (214a) of the first chamber (21) and the first matching wall (222) of the second chamber (22) are to be joint together at their outer edges by a first circumferential weld (411), and the second portion of the matching wall (214b) of the first chamber (21) and the first matching wall (235) of the third chamber (23) are to be joint together at their outer edges by a second circumferential weld (412), and the second matching wall (224) of the second chamber (22) and the second matching wall (232) of the third chamber (23) are to be joint together by a third circumferential weld (413).

15. The kit according to claim 14 wherein the first circumferential weld (411) and the second circumferential weld (412) are to form a continuous weld around the outer edges of the matching wall (214) of the first chamber (21).

16. The kit according to any of claim 13-15, wherein the matching wall (214) of the first chamber (21), the first matching wall (222) and the second matching wall (224) of the second chamber (22) and the first matching wall (235) and the second matching wall (232) of the third chamber (23) each comprises locating grooves (510).

17. The kit according to any of claim 12-14, wherein the first chamber (21) has a larger volume than the second chamber (22), and than the third chamber (23).

18. A method of manufacturing a sludge trap container (12) comprising the steps of:

- manufacturing a first chamber (21), a second chamber (22) and a third chamber (23) as independent and separate units, and wherein the first chamber (21) comprises a matching wall (214), the second chamber (22) comprises a first matching wall (222) and a second matching wall (224), and the third chamber comprises a first matching wall (235) and a second matching wall (232);

- assembling the first chamber (21), the second chamber (22) and the third chamber (23) so that: a first portion of the matching wall (214a) of the first chamber (21) is connected to the first matching wall (222) of the second chamber (22), the connected matching walls forming a first doubled-walled inner wall (321), a second portion of the matching wall (214b) of the first chamber (21) is connected to the first matching wall (235) of the third chamber, the connected matching walls forming a second doubled-walled inner wall (322), and wherein the first doubled-walled inner wall (321) is arranged adjacent to the second doubled-walled inner wall (322) along the plane of the matching wall (214) of the first chamber (21), the second matching wall (224) of the second chamber (22) is connected to the second matching wall (232) of the third chamber (23), the connected matching walls forming a third doubled-walled inner wall (323) of the sludge trap container (12);

- joining the first portion of the matching wall (214a) of the first chamber (21) and the first matching wall (222) of the second chamber (22) on their outer surfaces by a first circumferential joint (411); and joining the second portion of the matching wall (214b) of the first chamber (21) and the first matching wall (235) of the third chamber (23) on their outer edges by a second circumferential joint (412); and joining the second matching wall (224) of the second chamber (22) and the second matching wall (232) of the third chamber (23) on their outer edges by a third circumferential joint (413).

19. The method according to claim 18 wherein the matching wall (214) of the first chamber (21) and the first matching wall (222) of the second chamber (22) are on their outer surfaces welded by a first circumferential weld; and the matching wall (214) of the first chamber (21) and the first matching wall (235) of the third chamber (23) are on their outer edges welded by a second circumferential weld (412); and the second matching wall (224) of the second chamber (22) and the second matching wall (232) of the third chamber (23) are on their outer edges welded by a third circumferential joint (413).

20. The method according to any of claims 18 or 19 wherein the first chamber

(21), the second chamber (22) and the third chamber (23) are manufactured as independent and separate units using rotational casting.

21. The method according to any of claims 18-20, wherein the step of assembling the first chamber (21) with the second chamber

(22) and the third chamber

(23) comprises using locating grooves (510) that are provided on the matching walls (214; 222; 224; 232; 235).